1. Field of the Invention
This invention relates to a fully automated gel electrophoresis system using fluorescence detection capillary array electrophoresis for analyzing a large number of biological samples such as DNAS, RNAs, peptides, and proteins.
2. Description of the Related Art
With the advance of genome project, there is a growing demand for a high-speed and high-throughput DANA analysis system. Fluorescent DNA sequencers employing gel electrophoresis for separating DNA fragments have been used for DNA sequencing as well as DNA fragment analysis. These conventional systems use a slab gel plate made of polyacrylamide gel sandwiched between two plates. As to the shape of the gel, there are slab gels and gels packed in capillary tubes. In conventional systems, troublesome gel exchange should be manually carried out for each measurement. Therefore, there has been a desire for the development of a fully automated system in which gel exchange is fully automatically carried out. A promising method for full automation and rapid and high-throughput analysis is a capillary gel electrophoresis using a narrow capillary packed with a separation medium. The use of capillary array gel electrophoresis permits high-throughput and rapid DNA analysis because this electrophoresis can use a large number of electrophoresis lanes capable of analyzing many samples and can be rapidly carried out by applying a high electric field without a large amount of Joule's heat. The separation part in this electrophoresis system is composed of a capillary array and it is much easier to handle than slab gel plates because the capillary array is lighter than the slab gel.
On the other hand, there has been reported a method using a polymer gel as a separation medium in place of a cross-linked polyacrylamide. In systems using capillary tubes, there is a growing tendency that the same capillary tubes are repeatedly used after evacuating the used polymer gel and packed with fresh polymer gel. In these systems, after the completion of a measurement, the used polymer gel is pushed out of the capillary tubes to be replaced by fresh polymer gel and the next measurement is automatically carried out.
In electrophoresis separation and measurement, pre-electrophoresis or pre-running is carried out at first by applying an electric current to a gel without injecting DNA samples. The pre-electrophoresis is a cleaning-up process of the gel or a separation medium to remove impurities disturbing fluorescence measurements. Then, samples such as fluorophore-labeled DNA fragments are electrically injected into the separation medium. After the injection, electrophoresis is carried out at a constant voltage to separate the DNA fragments according to their length, and the DNA fragments are optically detected by fluorescences emitted from the DNA fragments at a detection portion several tens centimeters apart from the injection portion.
Examples of fluorescence detection electrophoresis analyzers of prior art have been disclosed in U.S. Pat. No. 5,529,679, U.S. Pat. No. 5,062,942 and U.S. Pat. No. 5,162,654.